Incandescent lamp



Patented Feb. 26, T952 UNITED STATES PATENT OFFICE 2,587,169 nvcANsENT LAMP John L. Kivarl', Detroit, Mich. Application August 3o, 1949; serial No. 113,090

afclaims. l(ci. ais-70) invention relatesv to incandescent lamps-,-

and more particularly to incandescent electric lamps of the screw-base type.

A main object of the invention is toprovide a novel and improved incandescent lamp adapted for use with ordinary house-lighting circuits,y said lam-p employing a low-voltage lament and including means for reducing the line voltage to a relatively low voltage for application to'l said filament. y

A further object of the invention is to provide an improved incandescent lamp which is characterized by relatively highlight output efficiency, which is very durable, and which has a useful life which is not affected to any serious extent by fluctuations Yin the house-lighting line voltage.

Further objects and advantages of the invention will become apparentv from'the following description and claims, and from the accompanying drawings, wherein:

Figure 1 is a side elevational view, partly in cross-section, of an improved incandescentv lamp constructed in accordance with the present invention;

Figure 2 is a schematic diagram illustrating the electrical connections of the lamp of Figure 1';

Figure 3 is an enlarged perspective detail view, showing a modied form of filament member constructed in accordance with the present invention;

Figure 4 is a cross-sectional detail view taken on line 4-4 of Figure 3.

Referring to the drawings, II generally designates an incandescent lamp, said lamp comprising an outer glass envelope I2 secured to a conventional screw-base I3, and enclosing a filament I4. As shown in Figure 1, the neck of the envelope I2 includes a transverse vglass partition member I5 on which is mounted the glass riser I6 containing the lead-in wires I I and I8. The filament I4 consists of a thin Tungsten circular shell transversely of and in encircling spaced relation with respect to the riser I6 and welded or otherwise rigidly secured at diametrically-opposite points to the respective lead-in wires I1 and I8. The lead-in wires II and I8 are relatively stiff, whereby the filament shell I4 is rigidly supported by said lead-in wires. Secured in the compartment dened in the neck of the envelope I2 below the glass partition wall I5 is a step-down transformer I9 whose secondary terminalsy are connected to the lead-in wires I1 and I8. One of the terminals of the primary of transformer vI9 is connected yby a wire 20 to the center contact 2I of the screw-base I3. The other secondary terminal of the transformer is connected by a wire 2 22 to the shell of saldi screw-base. The wiring connections are diagrammatically shown in Figi ure 2,.

In operation, the input line voltage, say,

volts A. C., is impressed across the primary of the. transformer I9, providing lo'w voltage, of the order of one volt, across the secondary of the transformer. The secondary voltage is impressed on the thin Tungsten ring I4. causing said ring to be heated to incandescence. The ring I4 has a relatively large surface area, and, therefore, provides a very large. light output, the voltage applied thereto and the thickness thereof being` such as to produce a highecurrent density in said ring, and to maintain the ring at a relatively high temperature. rAlthough a high current ows in the secondarycircuit of the transformer I9, the current in the primary circuit is not excessive. due to the stepf-dow-n characteristics of the transformer, and sincel the transformer eciency is relatively high, thereris little loss due to the use of said transformer.

- Figures 3 and 4 illustrate an alternative lament. member comprisinga cylindrical sleeve 23, formed of thin Tungsten or theY like and provided with internal stiifening rings 24, 24 at its respective ends. The sleeve 23 is connected to the leadin wires I'I and I8 at its respective end portions transversely of and in perpendicular spaced relation with respect to the riser and is supported on the lead-in wires in the same manner as the rings I4 are supported on said wires in the embodiment illustrated in Figure l. The thin filament sleeve 23 is heated up to incandescence by the secondary voltage applied thereacross from the transformer I9, a relatively high-current density being present in the sleeve, whereby a high operating temperature is obtained. Due to the large area of the sleeve, a very high light output is obtained per watt dissipated in the primary circuit of the transformer.

It is well known that the life of an ordinary incandescent lamp connected directly across the line of a house-lighting circuit may be severely reduced when the line voltage surges even momentarily, such surges frequently causing the lamp to immediately burn out. It has been found that the life of a lamp decreases very rapidly when the voltage applied across the lament is only a very small value above its rated voltage. By providing the step-down transformer I9 in the lamp, the actual change of voltage across the lament of the lamp is very small as compared with the amount of voltage above rated value which a line surge may cause across the primary of the transformer. Also, by employing the ring mechanically and will withstand severe shocks Y and vibratory forces, greatly increasing the mechanical durability of the lamp.

While certain specific embodiments of an incandescent lamp have been disclosed in the foregoing description, it is to be understood that various modifications within the spirit of the invention may occur to those skilled in the art. Therefore, it is intended that no limitations be placed on the invention except as dened by the of the appended claims.

What is claimed is: I

1. An incandescent lamp comprising a screw base and including a pair of contact terminals, a glass envelope secured at one end to said base, a partition xedly positioned transversely of and -within said envelope and spaced from said base, a step-down transformer including a primary and secondary positioned Within said envelope intermediate said partition and base and having. the primary connectedvat the opposite ends thereof to said Contact terminals, a riser positioned in the envelope and having one endsecured to said partition, a pair of lead-#in Wires positioned in said riser and projecting from the opposite ends thereof, one of the projecting ends of said lead-in wires being secured to the secondary of said transformer, and an annular filament positioned transversely of and spaced from said riser adjacent the other end thereof and secured to the other projecting ends of said lead-in wires.

2. An incandescent lamp comprising a screw base and including a pair of contact terminals, a glass envelope secured at one end to said base, a partition iixedly positioned transversely of and within said envelope and spaced from said base, a step-down transformer including a primaryand secondary positioned within said envelope intermediate said partition and base and having the primary connected at the opposite ends thereof to said contact terminals, a riser positioned in the envelope and having one end secured to said Scope' partition, a, pair of lead-in wires positioned in said riser and projecting from the opposite ends thereof, one of the projecting ends of said lead-in wires being secured to the secondary of said transformer, and an annular filament transversely of and in encircling spaced relation with respect to said riser adjacent the other end thereof and secured to the other projecting ends of said leadin wires.

3. An incandescent lamp comprising a screw base and including a pair of contact terminals, a glass envelope secured at one end to said base, a partition xedly positioned transversely of and within said envelope and spaced from said base. a step-down transformer including a, primary and secondary vpositioned within said envelope intermediate said partition and base and having the primary 'connected at the opposite ends thereof to said contact terminals, a riser positioned in the envelope and having one end secured to said partition, a pair of lead-in wires positioned in said riser and projecting from the opposite ends thereof, one of the projecting ends of said lead-in wires being secured to the secondary of said transformer, and an annular filament transversely of and in perpendicular spaced relation with respect to said riser adjacent the other end thereof and secured to the other projecting ends of said leadin wires.

JOHN-L. KIVARI,

REFERENCES CITED The following references are of record in the iile of this patent:

UNITED STATES PATENTS France Aug. 1, 1916 

